Athletes, exercisers, and physical-therapy patients (“users”) often use exercise equipment to increase muscle mass, increase cardiovascular fitness, and/or aid with muscle rehabilitation. Many users prefer to use free weights because a large variety of exercises may be performed using free weights and because free weights may be less expensive and need less storage and usage space than other types of exercise equipment. Additionally, free-weight exercises allow a user to move weights without restrictive poles, weight-and-pulley systems, and other types of guidance systems commonly used by exercise equipment. Accordingly, in addition to promoting power, strength, and athletic performance, free-weight use may also promote balance, and posture by developing stabilizing muscles.
Three commonly-used types of free weights are dumbbells, barbells, and kettlebells. Dumbbells are typically one-handed free weights. Accordingly, exercises performed with dumbbells are generally performed by either gripping a single dumbbell with one hand, or gripping a pair of dumbbells with two hands. Dumbbells may be adjustable or fixed-weight. FIG. 1A shows two exemplary adjustable dumbbells. In FIG. 1A, two adjustable dumbbells 100 and 101 are shown. The adjustable dumbbell 100 includes a central handle 102 for gripping the adjustable dumbbell 100, a first removably-attached grouping of variably-sized weight plates 104 in proximity to a first end of the central handle 102, and a second removably-attached grouping of variably-sized weight plates 106 in proximity to a second end of the central handle 102. Typically, the first removably-attached grouping of variably-sized weight plates 104 and the second removably-attached grouping of variably-sized weight plates 106 are of approximately equal weight and the length of a gripping surface on the central handle 102 is typically not much longer than the width of a user's hand. FIG. 1B shows an exemplary fixed-weight dumbbell. A fixed-weight dumbbell 108 includes a relatively short central handle, or core 110, for gripping the fixed-weight dumbbell 108 and permanently-attached weight knobs 112 and 114 at the opposite ends of the core 110.
A user may focus exercises, using either an adjustable or a fixed-weight dumbbell (“dumbbell”), on specific areas of the user's body. FIG. 2 shows a series of exemplary exercises performed using one or more dumbbells. Examples of different exercises that may be performed using a dumbbell include: (1) a flat bench dumbbell press 202; (2) a flat bench dumbbell fly 203; (3) an incline dumbbell press 204; (4) a single arm dumbbell row 205; (5) a shrug 216; (6) a seated dumbbell press 207; (7) a side lateral raise 208; (8) a seated alternate dumbbell bicep curl 209; and (9) a bicep concentration curl 210. In each of the exercises 202-210, each dumbbell is gripped by a central handle, which is maintained approximately in a horizontal orientation.
A user's grip around a central handle with a gripping surface not much longer than the width of a user's hand limits the number of available hand-gripping positions. Exercises performed using dumbbells are typically performed either using relatively low-weight dumbbells and/or maintaining dumbbells in a position such that a central handle is approximately in a horizontal orientation so as to maintain a user's wrist in a relatively straight orientation to reduce potential strain and injury. FIG. 3 shows a series of exercises performed using dumbbells involving potentially unsafe wrist twisting. FIG. 3 shows a user 302 performing a tricep dumbbell press 304 and a tricep kickout 306. When performing the tricep dumbbell press 304 or the tricep kickout 306, the user 302 may twist his or her wrist. Twisting of a wrist may lead to strain and injury. In addition, because a user typically grips a dumbbell around a relatively short central handle, group exercises, which involve passing a dumbbell between two or more users, and single-user exercises in which a user grips a dumbbell with two hands, may be difficult to perform. Furthermore, due to a limited number of available hand positions, exercises utilizing movements which employ several different hand positions, such as dynamic exercises, may be difficult to perform using a dumbbell.
Barbells are typically two-handed free weights. Exercises performed with barbells are generally performed by a user gripping a single barbell with two hands. FIG. 4 shows an exemplary barbell. A barbell 400 includes a central handle 402 for gripping the barbell 400 with two variably-spaced hands, a first group of variably-sized weight plates 404 in proximity to a first end of the central handle 402, and a second group of variably-sized weight plates in proximity to a second end of the central handle 402. As with dumbbells, the first group of variably-sized weight plates 404 and the second group of variably-sized weight plates 406 are typically of approximately equal weight.
FIG. 5 shows a series of exemplary exercises performed using barbells. Some exercises that may be performed using a barbell include: (1) a bench press 502; and (2) a barbell squat 504. Barbells are often heavier than dumbbells and, due to the relatively-long length of the central handle of a barbell, may be less stable and may create more torque while lifting. Consequently, barbell users often utilize a spotter to help avoid injury in the event that the barbell user is unable to maintain control of the barbell. The relatively-long length of a central handle for a barbell allows for more hand positions than a dumbbell. Therefore, dynamic exercises may be performed with barbells. However, the relatively-long length of a central handle for a barbell may make it difficult for a user to perform exercises involving horizontal twisting of the central handle, or exercises where the central handle of the barbell is positioned in an approximately perpendicular orientation. Additionally, the relatively-long length of a central handle may necessitate the use of a large amount of space for performing exercises.
Kettlebells are typically one-handed free weights. Kettlebell exercises are generally performed by either gripping a single kettlebell with one hand, or gripping a pair of kettlebells with two hands. FIG. 6 shows an exemplary kettlebell. A kettlebell 600 includes a ball with a flat bottom 602 attached to a curved handle 604 for gripping. The shape of a kettlebell creates a center of gravity low on a user's arm, enabling the user to safely perform exercises involving the twisting of the user's wrist, such as the wrist-twisting exercises shown in FIG. 3. Consequently, exercises performed with kettlebells may be dynamic, powerful, and explosive. FIG. 7 shows a series of exemplary exercises performed using one or more kettlebells. Some exemplary exercises that may be performed using one or more kettlebells include: (1) a kettlebell clean 702; (2) a single arm kettlebell row 704; (3) an alternating floor press 706; (4) a single arm kettlebell jerk 708; (5) a kettlebell swing 710; and (6) a kettlebell windmill 712. The ability to perform body motions that include wrist twisting allows a user to rapidly transition between a plurality of exercises, resulting in increased cardiovascular fitness and greater overall strength.
However, the configuration of a kettlebell often makes it difficult for a user to grip one kettlebell with two hands, limiting the gripping options available to the user. In addition, the orientation of a user's grip on a curved handle makes it potentially unsafe for a user to transfer a kettlebell to another user while performing group exercises. Kettlebells are also not readily available in a wide range of weights. Athletic trainers, coaches, physical therapists, and users have, therefore, recognized a need for compact free weights that allow a user to safely perform a large number of different exercises, including one-handed exercises, two-handed exercises, dynamic exercises involving wrist-twisting, and exercises involving the passing of exercise equipment between two or more users.